The present invention relates to an anti-loosening device for a drum tensioner bolt.
A user fastens tension bolts to the lugs to attach a drumhead and a hoop to an open end of the shell. After attaching the drumhead, the user adjusts the tension of the drumhead by adjusting the degree of tightening of the tension bolts. However, vibrations generated during drumming can loosen the tension bolts, reducing the tension of the drumhead and changing the sound of the drum.
In this respect, a tension bolt anti-loosening device 100 as shown in FIGS. 8A and 8B is proposed. To prevent loosening of a tension bolt after adjusting the tension of the drumhead, the anti-loosening device 100 is attached to the bolt head TBH of the tension bolt and fitted between the bolt head TBH and the hoop H. When readjusting the tension of the drumhead, the user adjusts the degree of tightening of the tension bolt after removing the anti-loosening device 100 from the bolt head TBH, or with the anti-loosening device 100 attached to the bolt head TBH.
U.S. Pat. No. 6,459,026 proposes another example of a tension bolt anti-loosening device that is used with a specialized tension bolt. The anti-loosening device includes an upper annular section, which accommodates the bolt head, and a lower tubular section, which receives the shaft of the tension bolt. The upper annular section consists of four separate walls located on the outer circumference of the bolt head. The lower tubular section is configured to be fitted into an elongated hole formed in the hoop.
The bolt head includes a flange, which is brought into contact with the upper surface of the lower tubular section of the anti-loosening device. The outer circumferential surface of the flange includes serrations, which engage the inner circumference surface of the upper annular section of the anti-loosening device. The engagement between the lower tubular section and the elongated hole of the hoop limits rotation of the anti-loosening device relative to the hoop. In addition, the engagement between the serrations of the flange and the inner circumference surface of the upper annular section limits rotation of the tension bolt relative to the anti-loosening device. Such structures prevent loosening of the tension bolt while drumming.
However, the conventional anti-loosening devices have the following problems. When tuning the drum before drumming, the user frequently adjusts the degree of tightening of the tension bolt while attaching and removing the anti-loosening device to and from the tension bolt, or with the anti-loosening device attached to the tension bolt. Thus, when the anti-loosening device 100 shown in FIGS. 8A and 8B is used for a tension bolt having a bolt head TBH of a tetragonal cross section, for example, the corners of the bolt head TBH tend to deform and enlarge the circular hole 100a. Accordingly, the effect of the anti-loosening device 100 to limit loosening of the tension bolt gradually degrades in use.
Further, if the size of the corners of the bolt head TBH is small and thus the engagement between the corners of the bolt head TBH and the inner circumference surface defining the circular hole 100a is insufficient, the anti-loosening device 100 fails to properly limit loosening of the tension bolt. Moreover, if the anti-loosening device 100 is attached to a lower tension bolt, the anti-loosening device 100 tends to fall off the bolt head TBH. If the size of the corners of the bolt head TBH is large and thus the engagement between the corners of the bolt head TBH and the inner circumference surface defining the circular hole 100a is excessive, it would be difficult to perform the attachment and removal of the anti-loosening device 100 to and from the bolt head TBH and the adjustment of the degree of tightening of the tension bolt performed with the anti-loosening device 100 attached to the bolt head TBH.
The anti-loosening device disclosed in U.S. Pat. No. 6,459,026 publication requires a specialized tension bolt and a hoop with elongated holes to function as an anti-loosening device of a tension bolt. That is, the anti-loosening device is usable only with limited types of tension bolts and hoops. This reduces the versatility as an anti-loosening device for a tension bolt. In addition, once the anti-loosening device of the publication is attached to a tension bolt, the anti-loosening device is not removable from the tension bolt since the lower tubular section of the anti-loosening device is placed under the flange of the tension bolt.